1. Field of the Invention
The present invention relates to a method for measuring behavior of a golf club to be swung by a golf player and that of a hit ball, and a system thereof.
2. Description of the Related Art
Measurement of behavior of a golf club and behavior of a golf ball is useful in confirmation and improvement of swings, fitting of a golf club which is fit for a golf player, designing and development of a golf club and a golf ball (hereinafter simply referred to as a ball) and the like. Thus, such a measurement system has been used in a golf practice range, a store, a manufacturer, and the like. Prior-art documents disclose various systems for measuring behavior of a golf club or behavior of a ball.
In Japanese Patent No. 2950450 (U.S. Pat. No. 5,471,383), as a measurement system for behavior of a ball, two cameras photograph balls immediately after being hit. Position information obtained through photographing is converted into three-dimensional coordinates to measure behavior of a ball. Japanese Patent Application Publication No. 2001-264016 (US2001/0023209) discloses a system for measuring motions of a ball by configuring a moving ball as images on a one-image frame. Japanese Patent No. 4109075 (US 2004/0076311) discloses a measurement method for identifying a position and a posture of a ball by displacing a position and a posture of an imaginary sphere in such a way that information of imaginary coordinates and the position and posture information of the photographed ball are coincident with each other. Japanese Patent Application Publication No. 2005-291824 (US2005/0233816) obtains first image information and second image information of a ball at different times. A method for measuring behavior of a ball in which the first image information and the second image information are mapped to the surface of a virtual spherical body, and behavior of the ball is measured from correlation of the two pieces of image information is disclosed.
An apparatus and a method for analyzing behavior of a golf club are disclosed in, for example, Japanese Patent No. 2826697, Japanese Patent No. 2950450, Japanese Patent No. 4109076 (US 2003/0228070), Japanese Patent No. 4307511, Japanese Patent Application Publication No. 2007-167549 and the like.
Japanese Patent No. 2826697 discloses an apparatus for measuring motions of a club head. The apparatus multiply images marks provided on at least three parts on a face surface of a club head from mutually different directions, extracting the marks from multiple imaged images, and obtaining three-dimensional coordinates of the above-mentioned marks from two-dimensional coordinates of the extracted marks.
Japanese Patent No. 2950450 discloses a monitor system for measuring flight characteristics of a moving object and an apparatus constituting the system. The system includes at least two cameras capable of photographing three or more target parts attached to a moving object which flies, and image digitalizing means for determining a pathway, velocity, and rotation in initial part of flight of the moving object in response to analog signals from the photographed target parts.
Japanese Patent No. 4109076 discloses a method and an apparatus for measuring an amount of rotation and a direction of a rotation axis of a curved solid. The measuring method obtains multiple two-dimensional images by photographing a rotating curved solid to which multiple marks are attached, at several points in time with a predetermined interval of time. On the one hand, a computer creates an imaginary curved solid on a surface of which multiple marks are attached similarly to the rotating curved solid mentioned above, in a space of three-dimensional coordinates. The computer displaces a posture of the imaginary curved solid so that the marks on the two-dimensional image surface match the marks on the imaginary curved solid surface. The amount of rotation and the direction of the rotation axis of the curved solid are determined by calculating a rotating matrix associated with a rotation operation of the imaginary curved solid during displacement, on the basis of the amount of displacement.
Japanese Patent No. 4307511 discloses a behavior measurement method and a behavior measurement apparatus of a moving object. In the measurement method, multiple marks provided on a moving object are multiply photographed from at least two different directions continuously at several points in time with a certain interval of time. A three-dimensional shape model of the moving object is created. Points (corresponding points) on the three-dimensional shape model corresponding to the photographed marks are identified. Time series data of positions and orientations of the three-dimensional shape model is calculated from the corresponding points on the three-dimensional shape model.
Japanese Patent Application Publication No. 2007-167549 discloses a method for analyzing behavior of a club head. In the analysis method, strobes are flashed with the timing depending on a swing rate of a golf club, the club head is multiply photographed by at least two cameras from mutually different directions, and behavior of the club head is determined from the multiple pieces of image information.
The measurement systems disclosed in Japanese Patent No. 2950450, Japanese Patent Application Publication No. 2001-264016, Japanese Patent No. 4109075, and Japanese Patent Application Publication No. 2005-291824 do not measure behavior of a golf club although they measure behavior of a ball. The systems do not figure out the behavior of the ball and the behavior of the golf club corresponding to the ball.
Although the apparatus disclosed in the above-mentioned Japanese Patent No. 282697 measures behavior of a club head before a ball is hit (impact), it neither measures nor calculates a positional relationship of the club head and the ball. Therefore, a hit point of the ball at the club head cannot be estimated.
The above-mentioned Japanese Patent No. 2950405 explains the DLT method that obtains three-dimensional data from multiple pieces of two-dimensional data of a golf ball as a moving object. Although the system disclosed in this publication can obtain a trajectory, velocity, and rotation in initial part of flight of a golf ball, it cannot obtain a positional relationship of the club head and the ball. Therefore, a hit point of the ball at the club head cannot be estimated.
The methods and the apparatuses disclosed in the above-mentioned Japanese Patent No. 4109076 and Japanese Patent No. 4307511 determine behavior of a target club head by using CAD data of a club head created on a computer. As the CAD data mentioned above does not perfectly match with a shape of an actual club head, a measurement error may occur. In addition, as CAD data of a club head is required, measurement is not easy. The methods and the apparatuses neither measure nor calculate a positional relationship of the club head and the ball. Therefore, a hit point of the ball at the club head cannot be estimated.
Although the above-mentioned Japanese Patent Application No. 2007-167549 describes “a face angle, a blow angle, a lie angle, and a hit point position (toe-heel direction, up-down direction) at impact”, it does not specifically disclose the method. It is needless to say that a hit point cannot be obtained in a quantitative manner.